The present invention relates to a system for the tracking control appropriate to a video tape recorder (hereinafter abbreviated to "VTR"). The system according to the present invention is especially appropriate for the so-called VHS Hi-Fi VTR which enables to record and reproduce audio signals with high quality by the audio head provided in addition to the video head in the type of the rotary head.
In such Hi-Fi VTR, a rotary head is composed of a rotatable drum, at least one audio head for recording and reproducing a carrier signal subjected to frequency modulation with a audio signal (hereinafter abbreviated to "an audio FM signal"), and at least one video head for recording and reproducing a carrier signal subjected to frequency modulation with a video signal (hereinafter abbreviated to "a video FM signal"), both heads being mounted on a circumference of the rotatable drum with a predetermined distance from each other.
First, by the audio head in the rotary head, the audio FM signal is recorded on the recording track for the video FM signal, and subsequently, by the video head in the rotary head, the video FM signal is superposedly recorded on the same track as the track on which the audio FM signal has been recorded. Namely, the audio FM signal is first recorded, and the video FM signal is subsequently superposed thereon. The audio FM signal is recorded down to the depths of the magnetic layer of the magnetic tape, whereupon the video FM signal is recorded on the surface of the magnetic layer of the magnetic tape.
Up to this time, concerning the system for the tracking control of the rotary head in a Hi-Fi VTR of the VHS type, there is a system in which the tracking error is detected based on the level of the video FM signal reproduced by the video head included in the rotary head, however in such a system the audio head in the rotary head is not necessarily controlled to the optimal tracking state. Namely, the head width of the video head is generally wider than the width of the video track on which video signals are recorded by the azimuth recording method, hence a certain admissible range can be set for the tracking control of the video head. However, because the head width of the audio head usually equals to the width of the track for recording signals, admissible range can not be set differing from the case of the above mentioned video head. As the result, in the above mentioned system in which the tracking error is detected on the basis of the video FM signal reproduced by the video head, the audio head may be out of the optimal tracking state even if the video head is in the admissible range for the tracking control, and as the result, the system has a defect that the S/N ratio of the audio signals reproduced by the audio head may be worse.
Hence, in order to eliminate such a defect, it can be considered to detect the tracking error of the rotary head on the basis of the audio FM signal reproduced by the audio head instead of the video FM signal reproduced by the video head, but in this case it becomes to a problem that the audio FM signals do not always exist differing from the video FM signals and the normal tracking control operation may be impossible while the audio FM signals do not exist (no sound periods).